A launder design method for thickened tailings

Abstract

In mountainous terrain, thickened tailings slurries are often transported by gravity flow in open channel launders (also called channels or flumes). These launders are typically constructed of concrete, and can run for many kilometres, as they transport the tailings slurry from the mine to a tailings storage facility at a lower elevation. Some of the large copper mines of Chile and Iran feature such launders, with some notable examples being Andina, Chile (57 km, carrying some 70,000 dry tonnes per day), Chuquicamata, Chile (15 km with 200,000 dry tonnes per day), El Teniente, Chile (86 km, 130,000 tpd) and Sarcheshmeh, Iran (16 km, 60,000 tpd). The main advantage of such launders is the ability to avoid pumping of the slurry. In mines such as these, the cost of pumping such vast amounts of tailings would be considerable. Launder cross-sections can come in many shapes, with common geometries being rectangular, trapezoidal and U-shaped. Circular pipes flowing partially full also function well as launders, and can offer certain advantages over the more common open-topped concrete sections. This paper presents a simple method for designing launders for the gravity transport of tailings slurries. The method applies to both Newtonian and non-Newtonian slurries, and works on the basis that the slurry flow maintains sufficient velocity to avoid deposition of solid particles in the launder. With inputs of flow rate, slurry concentration, rheology, particle specific gravity and particle size distribution, the design method calculates cross-sectional dimensions for a launder of rectangular, trapezoidal or circular cross-section, and then calculates a minimum slope required for the total transport of the slurry.